Method and apparatus for producing isotropic foamed stock

ABSTRACT

AN IMPROVED ONE-SHOT SYSTEM AND PROCESS FOR PRODUCING POLYURETHANE FOAM STOCK AND THE LIKE, INCLUDING MEASUREMENT CIRCUITS FOR DERIVING DIGITAL MEASUREMENTS OF PARAMETERS SUCH AS THE MASS TRANSFER RATES OF THE VARIOUS CONSITITUENTS, AND FURTHER INCLUDING AN AUTOMATIC CONTROLLER SYSTEM RESPONSIVE TO SUCH MEASUREMENTS FOR ADJUSTING AND CONTROLLING THE PARAMETERS WITH RESPECT TO PRESELECTED VALUES. A CONTROLLER SYSTEM IS PROVIDED FOR CONTINUOUSLY SAMPLING THE VARIOUS INCOMING MEASUREMENT SIGNALS SEQUENTIALLY, AND FOR DERIVING ERROR SIGNALS FROM A COMPARISON OF VARIOUS FUNCTIONAL RELATIONSHIPS OF THE SAMPLES RELATIVE TO PRE-ESTABLISHED OPTIMUMS. CONTROL CIRCUITS ARE ALSO INCLUDED FOR CONTINUALLY ADJUSTING THE OPERATION OF THE SYSTEM IN RESPONSE TO THE ERROR SIGNALS.

Sept. 21, 1971 c. PORTER ETAL 3,606,903

METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Filed Jan. 30, 1968 16 Sheets-Sheet 5 FIG 8 LAWRENCE c. PORTER a KENNETH E. GRAVES lf'vV/i/Vl (IRS in llzuwerf, Ma r? Uwllwe ATTORNEYS Sept. 21, 1971 L. c. PORTER ETAL 3,606,903

METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Filed Jan. 30, 1968 16 Sheets-Sheet 4 40A 40 FROM cONTROL- Dc RES/N FROM TANK 50A 48 38 MOTOR 50 N07 TO INDICATOR T [AR 0 BOARD Gfi VRSC {CGB-OX 47,4 47- M PAP/ FROM TANK N05 (LINE 73) 37A TO INDICATOR BOARD VRSC 8 FROM CONTROL SILICONE FROM MNK TO INDICATOR C; M NO. 3

'. Q 32 5 43A 0 52 6 B. FROM cONTROL- 9 43 cAT N07 FROM TANK IO 5522 0 VRSC 3N0. 2

FROM CONTROL TO INDICATOR T BOARD 4R PAPT FROM TANK N05 M Y (LINE 74) OAT No.2 FROM TANK TO INDICATOR 45\ M NO. 4 BOARD G 35 FROM OONTROL R PAPT F OM TANK N05 TO INDICATOR T 46\ M (LINE 15) t VRSCU- BOARD f 6 35 FIG. 9A LAWRENCE CPORTER a KENNETH E. GRA VES INVIL'N'I (IRS HY Amwaf Qm llume TO & Uwdwz ATTORNEYS I Sept. 21 1971 c. PORTER ETAL 3,606,903

METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Filed Jan. 30, 1968 16 Sheets-Sheet 5 88 FROM CONTROL- 1 76 D c cAsTOR OIL FROM 70 MOTOR\736 TANK NOZ/ A D 88A 76A OEAR 89 BOX 132 /60 FROM cON TROL I.

COLOR/N6 FROM 77 TO INDICATOR I m M TANK No.22 A BOARD I (D vRsc 89A 6 OLOR/N 7 98 137 B PUMP 1 FROM CONTROL- 78 PHOSPl-lOR/C ACID lO INDICATOR M \738 FROM MNK 98A 6 78A 99 BOA E 3 FROM CON TROL I 79 F/RE RETAROANT BOARD TO INDICATOR M \73 FROM TANK BOARD 3 6 9 NO./09

79A ESTA/IL: B

73A 75 FROM CONTROL 7 1 74 lfifffibi A INTEGRA7DR 7 v cONvERTER E2903; 5

75A- 0 fgw FLOW NJ- METER 7 TO INDICATOR 2 BOARD FREON RETURN To TANK NO 5 A7 37 A c. FREON FROM MOTOR TANK NO. 6

INVIiN'lURS m AWN, lGuA OT X? UwJwa ATTORNEYS Sept. 21, 1971 L. C. PORTER ETAL METHOD AND APPARATUS FORIRODUCING ISOTROPIC FQAMED STOCK Filed Jan. so, 1958 TO TANK o.1 80

16 Sheets-Sheet 6 LINE BLENDER ATTORNEYS RES/N fig; (77B 1 O TANK NO 5 87 E MAN/FOLD PREM/XER i PAPl-A g; 7 76 PAP/A TO TANK No.2 82 g A MAN/mail, SILICONE ROT. #92 76A ACT SILICONE TO TANK No.2 3 7 cAT. 1 ROT. W93 9 74h N Am cAT1 -15 O TANK No.5 94 HAPl-B ROT. /94

' Acr PAP/ B A To TANKNO.4 AT 2 RoT 74 AU CAT. 2 To TANK N05 86 PAP.-C ROT. -96

PAP/ c f To TANK N07 1 2' j CASTOR O/L- ROT. 756 75 To TANK N08 AU CASTROL OIL 753 F/ 1 COLOR/N6 ROT. A157 760 O COLOR/N6 TO TANK N09 7 4 PHOSPHOR/C ZCQTI /758 767 A PHOSPHOR/C 7 To TANK NOJO 1 ACID H3PO4 FIRE RETARDANT PO7'. -159 g FIRE RETARDANT 7 To TANK N06 87 LAWRENCE c. PoRTERa FREON ROT. A 97 KENNETH E. GRAVES ACT. INVIN'I()I BY M 1201M FREON I W & Uwuee 17 A Sept. 21, 1971 METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Filed Jan. 30, 1968 FROM cONTROL+ 16 Sheets-Sheet '7 OTOR 4 F RES/N FRO/W TANK NO. 7

786 lu TO scANNER FREO-TO OEAR FREO. CONV BOX 362 351 FROM CONTROL L M 41 r- AFRO/4 7 7 MNK NO. 5

7 98 Q "Hui J76 TO scANNER FREQ-TO- 6.

FREOcON. 165 B. 363 352 FRO CONTROL M ,42 F EQ QQQQ 139 EJ 177 NO3 TO scANNER FREQ-TO 6.

FREOcONv 766 B. 364 353 -FROM OONTROL+. M F ggTJA TQZNK 2 5 Q 173 NO2 TO SCANNER FREQ-TO- 6.

FREOcONv 767 B. 3 5 354 FROM OONTROLWT M 44 5315 BNISRSOM ln mm 779 TO SCANNER FREQ-TO- 6.

FREOcON. 168 B. 366 355 FROM CONTROL- }7-- M ggg O 9 mm 130 NO. 4 TO SCANNER FREQ-TO- 6. W,

367 FREQCONV 769 5.

TO SCANNER 356 FROM cONTROL- 4 RAM cFROM 28 792 M Q TANK NO. 5

FREO.-TO-' 6. FREO. OONv a LAWRENCE c. PORTER a FIG. 11A RENNE H E. GRAVES /VI',N/'()l S BY lbuwflf W 4% [Tu/bee ATTORNEYS L. C. PORTER ET L Filed Jan. 30. 1968 357 FROM CONTROL METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK 1e Sheets- Sheet a /736 cAsTOR OIL D. 0. FROM TANK MOTOR 782 NO. 7 r :n TO scANNER FgFgEa-Tgi/ 193 OEAR 369 O.cO 358 777/BOX COLOR/N6 FROM cONTROL M F FROM TANK 7 I J I NOB TO sOANNER /ggE O g m j PHOSPHORIC FROM CONTROL 58 AC) FROM TANK NO. 9 TO scANNER FREO-TO- J 795 I I 377- FREOOONv 360 773/ FROM cONTROL- M /739 RETAROANT 59 l 785 FROM 1 mm TO scANNER g g 61%; 796 G. T "T' 367 75 FROM CONTROL 1 VOLTAGE'TO' FREQUENCY INTEGRATOR 77 sERvO 73 CONVERTER MOTOR R241 70 gZ w FLOW TO SCANNER METER REG. \72 1 373 FREON 47 RET.

7 Ac FREON FROM MOTOR TANK No.6 3

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BY AMOM, nee,

W 9 Uunkee ATTORNEYS Sept. 21, 1971 L. c. PORTER ETAL 3,606,903

METHOD AND APPARATUS FOR PRODUCING ISO'IROPIC FOAMED STOCK Filed Jan. 30. 1968 16 Sheets-Sheet 9 T i FREoN PEG/289 TANK NO.6

FILTER o 297 REGENERAT/VE/ 298 TURBINE PUMP 1 FREO- TO 347 J To SCANNER FREQ. CONV 87 @7155 TURBINE FLOW F REG ME TE R SERVO FPOM CONTROL FIG FPO/ 7 CONTROL RES/IV FROM TANK NO.7

- 0c. 40 MOTOR GEAR 764 BOX 7 Pos/T/vE A m Q LDISPLACEMENT To SCANNER EREQ To FLOW METER 472 4/3 342 FREacoNv 7 I 1J7 L'AWRENcE cPoRTER 2 KENNETH E GRAVES B INVhNmRS 13y ll uwfif, Qowlanm,

\(mw (5 UunlQee ATTORNEYS Sept. 21, 1971 L. C. PORTER ErAL METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Filed Jan. 30, 1968 l6 Sheets-Sheet 1O 386 BI-D/RECT/ONAL 10 TuRN scR 350 sTERPER cONTROL CONTROLLER RES/N l L I TO SCANNER 6 387 375 1 Bl-D/RECT/ONAL 10 TuRN SCR 351 sTERPER CONTROL 1 OONTROLLER MOTOR POI PAP! -A 353 4 I TO SCANNER ,j

Bl-D/RECT/ONAL 70 TURN SCR 352 STEPPER cONTROL CONTROLLER J MOTOR POT SILICONE 364 E I TO SCANNER, 403 3/ 377 Bl-D/RECT/ONAL 70 TuRN scR is;

STEPPER cONTROL OONTROLLER MOTOR POT. CAT. NO. 1 365 TO SCANNER 6 3/90. 3

Bl-D/RECT/ONAL 70 TuRN scR 354 STEPPER OONTROL OON TROLLER MOTOR POT PAPl-B 366 i L TO sOANNER 4 1 8/ -D/RECT/ONAL- 70 TuRN SCR 5 sTERPER cONTROL OONTROLLER Wm. MOTOR POT. CAT. N02 367 To SCANNER 406 367 392 380 I T I I 356 B/- DIRECTIONAL 70 TuRN SCR 1 STEP/DER CONTROL OONTROLLER MOTOR POT- PAP/ C. 3 )53 To SCANNER L LAWRLN'LEEPORRL KENNETH E GRAVES T [3/6 13A I/N'V/iNH/RS BY Amofl Pug/hue,

Kwgez L? Uunkee ATTORNEYS Sept. 21, 1971 c; PORTER EI'AL 3,606,903 I METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Filed Jan. 30. 1968 16 Sheets-Sheet 11 407. 393 387 8/ OIRL OT/ONA 7 I R OR 357 L oTu N s STEPPER cO/vTROL cO/vTROLLER MOTOR POT CASTOR O/L 369 TO SCANNER Bl-D/RECT/ONAL 10 TURN scR 358 sTEPPER cO/vTROL CONTROLLER MOTOR POT cOLOR/A/O 370 TO SCANNER r Ell-DIRECTIONAL 70 TuR/v scR 359 STEPPER cO/vTROL cO/vTROLLER MOTOR POT PHOSPHOR/C ACID 371 L y g l R To SCAN/V5 410 531 395 384 360 B/- DIRECTIONAL 1o TuR/v scR 1 STEPPER CONTROL CONTROLLER MOTOR POT FIRE RETARDANT 372 A T TO SCANNER 367 Bl-DIRECTIONAL 70 TuR/v SERVO g STEPPER CONTROL AMPLIFIER MOTOR POT FREON 373 R I L TO SCANNE 373 FIG. I3 B LAWRENCE C.PORTER& KENNETH E GRAVES lNV/iN'H/RS 13y llzuwfif lwgea J1 Uwdfiee ATTORNEYS Sept. 21,

METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Filed Jan; 50, 1968 16 Sheets-Sheet 14 70 FIG. /5A FROM FIG. /5A

7 499 5// NO./ N0 2 42 1 HOLDING HOL D/NG 535 g: -K L REG/S TER REG/S TER gi- 369 CASTOR OIL cAsroR O/L Q C4570 535 P5557 2 RESET /vo./ No.2

524 555 OUTPUT 430 CO 0 /N HOLD/N6 HOLD/N6 L R G REG/STEP REGISTER REG/$75 I COLORING 1 COLOR/N6 x: 1 1 COLOR/N6 488/ A e 1,1,";

53 RESET N W RESET 5/3 50/ -477 NO./ 525 NO. 2 537 J OUTPUT 43/ PHOSPHOR/C HOLD/N6 g HOLDING JV RE G/S TE R 1 A00 REG/S TER REG/S 75R ag PHOSPH 3 7/ PHOSPH. ACID 7 PHOSPHAC/D :Nvvvv A00 459 f A M :1:

RESET RESET 5,

502 4 NO. 526 NO. 2 53a 4 OUTPUT 452 my; HOLDING HOL 0//vc :3 REGISTER I ,qfm o vr REG/STEP K REG/STEP F/RE FIRE R57. FIRE R57. RETARDAN,

490 F1 v v v v] 53 RESET a 2, Aj fi T RESET 5/5 3 f 503 J: NO. 527 NO. 2 OUTPUT 43a FREON HOL D/NG' HOLDING J 15333; REG/5 TEP REG/S TER REGISTER V f: 3 FREON 372 FREON FREON $313133 49/ /JZ3333J1331'2 l t I J I I I I I 539/ RESET: W W RESET 4a /475 477 475 I 7 2 57/2055 CLOCK GENERATOR f 434 "LA WRENCE C PORTER a FIG I58 KENNETH E. GRAVES INVh'N'l'URS BY 111m Mme ATTORNEYS 16 Shee ts-Sheet 16 DC I/OL774GE TO SCANNER SW/TCH AND .c 004 as HOLD F/ G. l 7

RESE T FREQ. OUT

L. C. PORTER L JVVU \SCHM/TT m NO./ RAMP GENERATOR TR/GGE R VOLTAGE COMPARISON RESET METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK (IIIIIIIIIIIIIII /vo 2 RAMP GENERATOR 335 RES/N PULSE TRAIN 40 MOTOR Sept. 21, 1971 Filed Jan. 30, 1968 STEP/35R BY Azuwfif Wee, DR/VER luu m 9 Own/Lee ATTORNEYS L. .J OSC/LLATOR- FREQ. H000 NETWORK v Ru v R 4 5 R 4 wm E w m R wfi m 5 %Am 5 N HW .R w 6 T 0m E 5 5 C FL. m 7 AL RN 6/0 R w J Mm P/U N M m LK F m c M m OCT W RwA w Cm U E m u R G R 5 III. E E W E m M 3 W U m E w 61 3 m H R 5 5 F L E 2 M w m M 5 5 T K QQQS 95%? 8508 M r- G603 mwfiiot 6m who w 5 m 9? omnbou omkw m. $03 6528 w W 6 O5 C/LLA TOR United States Patent 3,606,903 Patented Sept. 21, 1971 3,606,903 METHOD AND APPARATUS FOR PRODUCING ISOTROPIC FOAMED STOCK Lawrence C. Porter, Palos Verdes Peninsula, and Kenneth E. Graves, Saratoga, Calif., assignors to The Upjohn Company, Kalamazoo, Mich.

Filed Jan. 30, 1968, Ser. No. 701,596 Int. Cl. G05d 21/02 US. Cl. 137--88 33 Claims ABSTRACT OF THE DISCLOSURE An improved one-shot system and process for producing polyurethane foam stock and the like, including measurement circuits for deriving digital measurements of parameters such as the mass transfer rates of the various constituents, and further including an automatic controller system responsive to such measurements for adjusting and control-ling the parameters with respect to preselected values. A controller system is provided for continuously sampling the various incoming measurement signals sequentially, and for deriving error signals from a comparison of various functional relationships of the samples relative to pre-established optimums. Control circuits are also included for continually adjusting the operation of the system in response to the error signals.

BACKGROUND OF INVENTION This invention relates to the production of cellular synthetic resin stock, and more particularly relates to methods and apparatus for producing foamed synthetic resin stock, especially polyurethane foam, having a substantially rectangular cross section and which is generally isotropic in character.

It is well known to produce urethane foam stock by combining a suitable polyhydroxyl compound, a blowing agent such as Freon, and a polyisocyanate, to produce a foam which solidifies into a cellular material. It is also well known to at least partially confine such foam, during its hardening process, to produce stock (hereinafter referred to as bun) which is thereafter cut into smaller pieces or billets for sale to fabricators.

Depending upon the choice of the polyhydroxyl (hereinafter referred to generally as the resin), the bun can be made either rigid or flexible. The structure of urethane foams, whether rigid or flexible, consists of a network of cells which are preferably of a substantially uniform size and shape. In flexible foams, the cells are open. In rigid foams, however, the cell structure is closed. If the rigid foam material is intended for certain purposes such as thermal insulation, substantially uniform cell structure is greatly desired in order to provide uniform compressive yield strength characteristics which are substantially the same along the X, Y, and Z directional axes along which a force may be applied.

As hereinbefore mentioned, polyurethane foamis produced by the polymerization of the resin and the selected isocyanate. The Freon is added to produce the leavening effect which causes the resulting polyurethane mass to rise and to assume the cellular character sought to be obtained. Hence, all polyurethane foam manufacturing techniques generally comprise the steps of disposing the resin, isocyanate and Freon mixture, in a restricted or partially restricted enclosure to create a bun having generally preselected cross-sectional dimensions. More particularly, the liquid mixture of resin, isocyanate and Freon is preferably poured onto a moving conveyor (such as an endless belt) which carries the mixture into and through a tunnel-like enclosure or mold as it rises and solidifies. In other Words, the mixture rises within the tunnel, but

the cross-sectional dimensions of the tunnel tend to restrict the bun and give it the cross-sectional shape and dimension sought to be obtained, as well as to apply a preselected pressure to the foam to control the shape of the cells and thehomogeneity of the foam.

As the completed bun is carried out of the exit end of the tunnel, it may be cut into preselected lengths or billets which may then be sold to fabricators who will cut the billets into such shapes as may be desired by the ultimate consumers. However, since most of the billets are intended to be cut into slabs or planks which also have rectangular cross sections, it will be apparent that waste will occur unless the bun itself has a generally rectangular cross section, since any rounded or irregular side portions must usually be discarded.

Methods and apparatus for commercially producing an isotropic polyurethane bun having a preselected density and compressive strength, and also having a substantially rectangular cross section, have long been sought. Prior art techniques have succeeded in commercially producing buns which are generally satisfactory from the standpoint of density and compressive strength. Furthermore, buns having substantially rectangular cross sections have also been produced in commercial quantities, although only at a considerable effort, and at a cost which is not competitive with the cost of the nonrectan-gular buns. However, it has hitherto been impossible, with the methods and apparatus of the prior art, to commercially produce a rectangular bun having the desired density and compressive strength characteristics, and at a cost which is competitive with the price of nonrect-angular buns.

In addition to the basic foam constituents hereinbefore mentioned, it has been found desirable to include certain other materials in the mixture to produce a polyurethane foam having ideal properties. For example, a surfactant such as polyoxyalkylene-polydimethylsiloxane (hereinafter referred to as silicone) is usually included in selected amounts to regulate cell size and cell wall stability during foaming. Water is included in regulated amounts to give the foam the proper degree of flowability, during the leavening stage, so that the bun will fil-l the upper corners of the tunnel and thus assume a substantially rectangular cross section. Catalysts such as triethylamine and castor oil are also usually included in proper proportions to achieve the desirable balance between the foaming and polymerization reactions, and to control the speed of such reactions. Coloring substances may also be included in the resin isocyanate mixture.

Notwithstanding the use of these other catalysts and constituents, it should be appreciated that the basic reaction between the resin and the polyisocyanate is relatively quite rapid and is thus quite difficult to control during commercial manufacture of polyurethane bun. Although a one-shot process is theoretically the most efficient for the commercial manufacture of polyurethane, it has been found necessary for the most part to employ either semiprepolymer or complete prepolymer sys terns in order to produce an isotropic bun having the proper characteristics of density, compressive strength, rectangular cross-sectional configuration, etc. 4

The problem of using a one-shot process is further complicated by the fact that there are other materials used in producing polyurethane foam, besides the basic reactants, foaming agent, and catalysts hereinbefore mentioned. For example, coloring agents and fire retardants are often included. Although constituents such as these are generally thought of as non-reacting components, this is not strictly true since they are usually combined with base resin or other suitable resins comparable with the foam system. These resins are reactive and must be considered as part of the reactive system.

Another complication arises because of unavoidable variations in the purity and quality of the components. Due to economic limitations, the various constituents are of industrial grade and thus the character of the reaction may sometimes vary unexpectedly simply because a particular component has been taken from a different batch. In addition, changes in environmental parameters, such as humidity, temperature, and barometric pressure, may also affect the speed and character of the reaction, and the size and distribution of the cells in the resulting polyurethane foam.

Once the basic reactants (the resin and the isocyanate) have been physically combined, the resultant reaction will proceed relentlessly to a conclusion and the process can neither be halted, retarded or reversed. Thus, a oneshot process is difficult to control since the character of the reaction is largely apparent only in the finished polyurethane foam, although extermely skilled and experienced operating personnel can sometimes make very limited quality estimates from observation of certain physical characteristics of the reaction during intermediate stages of the process. Unfortunately, however, it is usually diflicult to determine within required limits the precise adjustment to be made, and thus it is usually necessary to stop all production completely for an hour or more each time it is necessary to make any adjustment in the proportions of the various constituents. Moreover, it is often necessary to make such an adjustment solely on the basis of empirical determinations, and thus it will be apparent that it is often necessary to stop and start a one-shot process several times before a satisfactory product can be produced.

Since the various factors which contribute to the character of the product are all either selectively controllable or capable of being counteracted, it has long been desired to develop a self-balancing system continually responsive to measured variations in each significant parameter according to a preselected relationship. For various reasons not immediately apparent to those unfamiliar with this art, however, no such system has previously been developed.

In the first instance, conventional control equipment is designed to operate on a system of binary numbers, whereas the various parameters needed to be controlled are measured for the most part in terms of mass transfer units, belt speed and the like. The language of binary numbers is not one with which operators of polyurethane foam systems are generally familiar, and thus it is necessary to mate the system controller to the system, rather than to mate the foam system indicator outputs to the controller, as is generally done with controllers of this class.

Another difficulty exists in the fact that the production system must be controlled with extreme precision, notwithstanding that line blending is involved in a one-shot system for producing polyurethane foam. Thus, it is desirable to use the inherent precision of digital logic for controlling the production system, since analog circnitry and systems are well known to be both expensive and difficult to operate with required precision for long periods of time. However, it is also expensive and complex to mate a digital system with a line blending operation since the handling and registering of fluid flow measurements is inherently incompatible with the basic concept of digital logic, and thus it is necessary to include extensive conversion circuitry with systems of the prior art.

These disadvantages of the prior art are overcome with the present invention, and novel methods and apparatus are provided herein for commercially manufacturing either flexible or rigid homogeneous polyurethane bun, which is isotropic, and which has such other preselected chemical and physical properties as may be desired. It is a feature of the present invention to provide novel methods and apparatus for commercially manufacturing flexible or rigid polyurethane bun having preselected charsection, of certain details of the apparatus depicted in 4 acteristics and properties by means of a one-shot process. It is a further feature of the present invention to provide a one-shot system employing a controller section responsive to continuously generated measurements of various selected parameters to continuously adjust and maintain productivity according to a preselected relationship. It is also a feature of the present invention to provide a system of the foregoing description including means for providing directly recordable signals for the purpose of quality control.

SUMMARY These advantages of the present invention are preferably obtained by novel methods and apparatus employing a one-shot system, wherein improved monitoring methods and apparatus are provided for directly and accurately indicating and regulating the proportions of the various constituents in terms of mass transfer units, for selectively adjusting the inclination angle of the tunnel during operation of the system and process, for raising and lowering the pour'mg spout and the input end of the tunnel as a unit in order to maintain a preselected spacing between the spout and the floor of the tunnel, for synchronizing the conveyor speed and the saw movement, and for providing lateral as well as vertical saw movement.

In addition, a novel controller section or circuit is preferably provided which receives the aforementioned measurements and compares them on the basis of a preestablished relationship, for the purpose of deriving correction or adjustment output signals functionally related to such comparison, and provision is included for rendering the production system responsive to such adjustment signals as will hereinafter be explained.

These and other features and advantages of the present invention will be apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings:

THE DRAWINGS In the drawings:

FIG. 1 is a basic flow diagram showing the mixing stages of the various constituents or ingredients utilized in a one-shot method and system of the type discussed herein for manufacturing polyurethane foam.

FIG. 2 is a pictorial representation of the major components of the preferred system employed for manufacturing polyurethane'billets by means of the present invention.

FIG. 3 is a pictorial representation, partly in cross section, of a portion of the system depicted in FIG. 2.

FIG. 4 is a pictorial representation of an end view of an isotropic polyurethane billet of the type produced by means of the present invention.

FIG. 5 is a pictorial representation of another portion of the system employed to produce polyurethane bun by means of the present invention.

FIG. 6 is a pictorial representation, partly in cross FIG. 5.

FIG. 7 is a pictorial representation, partly in cross section, of another portion of the apparatus depicted in FIG. 2.

FIG. 8 is a functional representation, partly pictorial, of another portion of the apparatus generally depicted in FIG. 2.

FIGS. 9A and 9B together provide a functional representation of a system for monitoring and controlling the mixing of the constituents generally depicted and represented in FIG. 1.

FIG. 10 is a functional representation of a further portion of the flow system generally depicted in FIG. 1.

FIGS. 11A and 11B together provide a functional representation of an alternative form of the circuitry and components represented in FIGS. 9A and 9B.

FIGS. 12A and 12B provide functional representations of additional alternative forms of selected portions of the circuitry represented by FIGS. 9A and 9B, and by FIGS. 11A and 11B.

FIGS. 13A and 13B provide a functional representation of a suitable circuit for coupling the circuitry illustrated in FIGS. 9A, 9B, 11A, 11B, 12A and 12B, to a suitable control and indicator section.

FIG. 14 is a functional representation of a suitable controller system useful for operating a production system of the type illustrated in FIGS. 1-13.

FIGS. 15A and 15B represent a more detailed functional representation of a portion of the system illustrated in FIG. 14.

FIG. 16 depicts the system illustrated in FIG. 14 during selected phases of'operation.

FIG. 17 depicts a more detailed functional representation of an exemplary portion of the structures illustrated in FIGS. 11A and 11B, and FIGS. 12A and 12B.

FIG. 18 depicts a more detailed functional representation of another selected portion of the system illustrated in FIG. 14.

DETAILED DESCRIPTION Referring now to FIG. 1, there may be seen a functional representation of ten separate tanks 1-6, 21, 22, 108 and 109, each holding a different constituent or i11- gredient, and each having its respective output line interconnected with either a manifold or line blender 11, or with a mixing nozzle 18, to provide a continuous or oneshot production of polyurethane foam 20. More particularly, it may be seen that in a suitable arrangement, Tank No. 1 holds resin. Tank No. 2 contains a first catalyst such as a suitable amine, Tank No. 3 contains silicone, Tank No. 4 contains a second catalyst such as a 50:50 mixture of water and a selected resin and Tank N0. 5 contains a suitable isocyanate such as polymethylene polyphenylisocyanate and hereinafter referred to as PAPI (a registered trademark of The Upjoin Company).

Tank No. 6 will preferably contain a suitable blowing or leavening agent such as Freon, Tank No. 7 contains castor oil, Tank No. 8 may contain a coloring agent or dye, and Tank No. 9 preferably contains phosphoric acid. It is a well known characteristic that polyurethane is flame resistant in contrast to similar materials such as polystyrene foam. However, this characteristic may be enhanced by the addition of a suitable fire retardant which may be contained in Tank No. 10.

The two basic reactants are located in Tanks No. 1 and 5', and although the substances in the other tanks may enter into and affect the reaction, they are effectively nonreactant with each other or with either of the two reactants separately. Hence, it is desirable as may be seen in FIG. 1 to connect the outputs of Tanks No. 1-4 via conduits 7-10, to a manifold or line blender 11, where they may be combined physically into a mixture having the desired proportions, before adding the other reactant. Accordingly, the mixing nozzle 18 is connected to only three input lines, i.e., those connected to the line blender 11, and Tanks No. 5 and 6, only.

More particularly, output lines 7-10 and 160463, respectively, of the tanks 14, 21, 22, 108 and 109' holding the resin 1, the first catalyst, silicone, the second catalyst, castor oil, coloring, phosphoric acid, and fire retardant, may be seen to be connected to deliver material into the line blender 11. The Freon is delivered from tank 6 into the mixing nozzle separately through line 17.

The PAPI preferably flows from Tank No. 5 into three separate output lines 1315, as will hereafter be made apparent, and which are connected to a suitable manifold (not depicted) having a single output line '16 connected to the mixing nozzle 18. After the various ingredients reach the mixing nozzle 18- in the proper proportions, they are thoroughly intermixed before they can interact, and the mixture is then ejected through a spout 19 to form into the polyurethane foam 20.

It should be remembered that the resin in tank 1 and the PAPI in tank 5- rapidly interact when commingled in the mixing nozzle 18. Furthermore, it should be noted that Freon tends to cause the other constituents in the mixture passing between the blender 11 and the mixing nozzle 18 to separate. Since the isotropicity of the resultant bun depends in large part upon the thorough intermixing of all constituents before the polymerization interaction can proceed to any substantial degree, it is an advantage to first intermix those constituents which do not interact (the resin, silicone, catalysts, etc.), and thereafter to intermix only three active ingredients or constituents in the mixing nozzle 18. Accordingly, this is why it is preferable to first intermix the constituents in tanks 14, 2 1, 22, 108 and 109 in the line blender 11, and then to combine only three separate constituents within the mixing nozzle 18 proper.

The flow of liquid Freon, from tank 6 to the mixing nozzle 18, may be provided by suitable pumping means as will hereinafter be described. Alternatively, tank 6 may be pressured by a nonreacting gas such as nitrogen, and the nitrogen pressure in tank 6 can be used to force the Freon into and through the mixing nozzle 18- and spout 19.

The various structures and techniques hereinafter described, may conveniently be separated into those dealing directly with the mixing'of the ingredients and the production of the resulting foam, and those dealing with the control of the operation. Hence, the description hereinafter following will arbitrarily be divided into those functions relating to production and those functions relating to control.

THE PRODUCTION SYSTEM Referring now to FIG. 2, there may be seen a functional and partly pictorial representation of an apparatus for receiving the mixture from the mixer spout 19 depicted in FIG. 1, and for forming the polyurethane foam into a proper bun. In particular, the production system may be generally defined as being comprised of three main components, i.e., the tunnel mold section 200, a transitional conveyor section 202, and a saw assembly 204. It is a function of the tunnel section 200 to receive the mixture of resin, PAPI, Freon, and the various catalysts and other ingredients, and to provide a mold wherein the mixture will foam up into a polyurethane bun having preselected dimensions and properties, and

to properly Wrap it in paper. It is the function of the transitional conveyor section 202, to conduct the finished and wrapped bun between the tunnel section 200 and the saw assembly 204, and it is the function of the saw assembly 204 to cut the finished and wrapped bun into polyurethane billets of a preselected length.

Referring now to the tunnel section 200, it may be seen in FIG. 2 to be generally comprised of a tunnel mold 210 having right and left side conveyor belts 119 (only one belt being depicted), a series of side panels 102 (only one side being depicted) disposed within the endless side belts, a bottom panel concealed within two bottom longitudinal struts 111 (only one strut being depicted), and a bottom conveyor belt 115, and a series of top panels 103 each supported by a truss-like frame 121 and support rod 125, and hidden between two top struts 220 (only one strut being depicted).

The concealed bottom and side panels are rigidly held in position to form the bottom and sides of the tunnel mold 210. The top panels 103 are adjustably positioned to provide a tunnel having a preselected height. However, as will hereinafter be explained in greater detail, each top panel 103 is spring-loaded downward so as to yield to excessive upward pressure of the bun in the tunnel.

It should further be noted that each top panel 103 is provided with a lower protruding lip 222, extending in the direction of movement of the bun through the tunnel mold 210 and projecting under the edge of the next adjacent top panel 103. This is provided so as to prevent thev top panel 103 from impeding travel of the bun through the tunnel mold 210.

Asmay be seen in FIG. 2, there is preferably provided an endless bottom conveyor belt 115 rotatably mounted on the front and rear rollers 25 8 and 260 so as to rotate about the bottom panel. This bottom conveyor belt 256 is preferably synchronized with the side conveyor belts 119, as will hereinafter be explained, so as to conduct the bun through the tunnel 210 towards its exit end 224.

As will further be explained in detail, it is necessary as well as desirable that the bun be completely Wrapped with paper or other suitable covering material as it passes out of the tunnel 210. Accordingly, a roll 230 of bottom paper 232 is shown mounted on a roller assembly 234, with the bottom paper 105 passing upward and over a top roller 236 and then downward and under a pair of creasing wheels 238, between two pairs of closely spaced, vertical support bars 240, whereby the bottom paper 105 assumes a U-shape as it passes under the spout 19 of the mixing nozzle 18. The two creasing wheels 23 8 are adjustably. spaced apart a distance substantially equal to the width of the tunnel mold 210 so that the U-shaped bottom paper 232 will fit into the tunnel mold 210 without wrinkling. Thus the mixture of resin, PAPI, etc. received from the spout 19 is poured onto the bottom paper 105 rather than directly upon the endless bottom belt 115.

A narrower roll 242 of top paper 106 is located on a second roller assembly 246 mounted on top of the tunnel mold 210. As may be seen, the top paper 106 is passed downward under a rotatable creasing roller 248 to be formed into a U-shape before passing into and through the tunnel adjacent the bottom and side surfaces of the top panels 218.

As will hereinafter be discussed in detail, the tunnel section-200 is preferably inclinable with its pivot point located at or adjacent its exit end 224. Furthermore, when the entrance end 250 of the tunnel mold 210 is raised or lowered in order to vary its inclination, means hereinafter described in detail are preferably provided for maintaining a constant preselected spacing between the spout '19 and the bottom surface of the tunnel mold 210.

Means are preferably provided to move the mixing nozzle 18 and spout 19 backward and forward laterally across the bottom paper 105 at the entrance end 250 of the tunnel mold 210 to thereby deposit a preselected constant stream of mixture evenly upon the bottom paper 105. The speed and traverse of the mixing nozzle 18 and spout 19 are preferably controlled to regulate the pattern of mixture being deposited, and the speed of the conveyor belts can also be selectively controlled, all to assist in regulating the volume of bun being produced. Moreover, the mixing nozzle 18 can be caused to dwell for a preselected interval, at the end of each traverse, so-as to further regulate the pouring pattern to insure homogeneity of the bun being produced.

As hereinbefore stated, the bottom conveyor belt 115 and the side conveyor belts 119 (only one being depicted) cooperate to draw the bottom paper 105 into the tunnel. Thus, the liquid mixture deposited from the spout 19' on the bottom paper 105 is carried into the tunnel during the interval wherein it tends to leaven or foam up at a preselected rate so as to fiow into the corners of the tunnel mold 210 and thus assume its proper shape and cellular form. When the foam has substantially filled the cross section of the tunnel mold 210, it tends to catch the top paper 106 and then draw the top paper 106 with it through the tunnel mold 210.

It should be understood that the volume or amount of polyurethane foam being produced is a function of the size and density of the bun. However, these characteristics, although controllable, are dependent upon many factors besides the proportions of the various constituents combined in the mixing nozzle 18. For example, factors such as the ambient temperature of the system, the flow rate of mixture from the spout 1 9 to the bottom paper 105, and the velocity of the lower belt 115, are also important. The ambient temperature of the system cannot ordinarily be easily controlled, but the flow rate of mixture into the system and the velocity of the lower belt 115, can and should be correlated and regulated.

If the speed of the lower belt is too fast, the foaming mixture will be carried through the tunnel 210 before the bun can be molded properly, and the resulting bun will not be rectangular. On the other hand, if the speed of belt 115 is too slow, the foam front of the rising mass will tend to back up in the tunnel mold 210 and roll back over fluid which has not yet begun to rise. In such a case, the resulting bun will contain irregularities and will obviously not be isotropic.

In addition, it is also desirable to adjust the system to keep the foam front as nearly flat as possible, since this will provide for foam at a constant rate, and since this will help provide for isotropicity of the resulting bun. Accordingly, the tunnel mold 210 may be selectively inclined at an angle such as to maintain a fiat or substantially flat foam front, in correlation with the speed of the lower belt '115 through the tunnel mold 210, and these parameters must be correlated with the flow rate (and constituency) of the mixture deposited by the spout 19.

As will be apparent from a study of FIG. 2, the finished rectangular bun passes out of the exit end 224 of the tunnel mold 210, and onto the roller bars 251 of the transitional conveyor section 202. The conveyor belts 119 and 115 in the tunnel assembly 200 push the bun across the roller bars 250, and onto the saw conveyor belt 252 in the saw assembly 204. It is a function of the saw conveyor belt 252 to carry the finished bun under the saw blade 254, and thereafter to carry the severed billets away from the saw blade 254.

It should further be noted that the bottom conveyor belt 256 is disposed about a front roller 258 mounted ahead of the pouring spout 19, and a rear roller 260 mounted immediately below the rear roller 262 which supports the side conveyor belt 212. Roller 260 is driven by an electric motor 264, and rotation of roller 260 may be seen to apply rotary power to roller 262 by means of beveled gears 266. It should be further noted that the saw conveyor belt 252 is disposed about front and rear rollers 270 and 272. The saw conveyor belt 252 is driven by power applied to rear roller 272 through a suitable drive belt 274 which is connected to a suitable electric motor 276. It is preferable that belt 252 be rotated in synchro nism with belts 256 and 212. Accordingly, motors 264 and 276 are preferably both controlled by the same control circuit 278.

It should be further noted that the saw 254 is mounted on a saw carriage 280 which operates to drive the saw blade 254 downward to sever each billet from the bun departing the tunnel mold 210 at its exit end 224. The saw blade 254 may be actuated downward by any suitable conventional means, such as by compressed air.

It should also be noted that the bun will continuously leave the exit end 224 of the tunnel, irrespective of the action of the saw blade 254. Accordingly, the saw carriage 280 preferably travels with the bun, as the saw blade 254 moves downwardly to cut off each billet. In this manner, the saw blade 254 will not impede movement of the bun out of the exit end 224 of the tunnel. Accordingly, the saw carriage 280 is preferably fitted with three rollers 282, 284 and 286, which permit the saw carriage 280 to move back and forth along the saw assembly 204 without impeding movement of the saw conveyor belt 252. More particularly, the belt 252 is disposed over rollers 282 and 286, and under roller 284, so that when saw blade 254 reaches the bottom of the bun it will not sever belt 252.

Upon completely severing the bun, however, the saw blade 254 immediately rises to the top of the carriage 280 and the carriage 280 then travels backwards over 

